1. Field of the Disclosure
The present disclosure provides a computer and computing capable of easily solving an NP-complete problem mapped into the ising model by easily solving the ising model.
2. Discussion of the Background Art
The ising model has been researched originally as a model of a magnetic material but recently attracts attention as a model mapped in an NP-complete problem or the like. However, it is very difficult to solve the ising model when the number of sites is large. Thus, a quantum annealing machine and a quantum adiabatic machine in which the ising model is implemented are proposed.
In the quantum annealing machine, after ising interaction and Zeeman energy are physically implemented, the system is sufficiently cooled so as to realize a ground state, and the ground state is observed, whereby the ising model is solved. However, in a case where the number of sites is large, the system is trapped into a metastable state in the process of being cooled, and the number of the metastable states exponentially increases with respect to the number of sites, whereby there is a problem in that the metastable state is not easily mitigated to the ground state.
In the quantum adiabatic machine, transverse magnetic field Zeeman energy is physically implemented, and then the ground state of the transverse magnetic field Zeeman energy is realized by sufficiently cooling the system. Then, the transverse magnetic field Zeeman energy is gradually lowered, ising interaction is physically implemented gradually, the ground state of the system that includes the ising interaction and vertical magnetic field Zeeman energy is realized, and ground state is observed, whereby the ising model is solved. However, when the number of sites is large, there is a problem in that the speed of gradually lowering transverse magnetic field Zeeman energy and physically implementing the ising interaction in a gradual manner needs to be exponentially decreased with respect to the number of sites.
In a case where the NP-complete problem or the like is mapped into an ising model, and the ising model is implemented as a physical spin system, there is a problem of a natural law that ising interaction between sites that are physically located close to each other is large, and ising interaction between sites that are physically located far from each other is small. The reason for this is that, in an artificial ising model in which the NP-complete problem is mapped, there may be cases where ising interaction between sites that are physically located close to each other is small, and ising interaction between sites that are physically located far is large. The difficulty in mapping into a natural spin system also makes it difficult to easily solve the NP-complete problem or the like.